PROJECT SUMMARY - ABSTRACT Fundamental behavioral processes such as associative learning, rate calculation and decision making crucially rely on estimation and reproduction of time intervals in the seconds-to-minutes range (interval timing). These processes are disrupted in Parkinson's disease, Huntington's disease, and Schizophrenia. This project will further our understanding of the disruptions of cognitive processes in these disorders by investigating the impact of characteristics of events on the ability to keep track of time. One of the underlying assumptions of most timing theories is that subjects are able to readily abstract from the input stimulus the temporal information, and to tune their behavior according to this cue, irrespective of non-temporal properties the real timed event. In contrast, evidence suggests that both animal and human timing is highly sensitive to properties of the timed signal. Such data support a resource allocation theory which posits that attentional and memory resources dedicated to interval timing may be re-allocated for other cognitive processes, which in turn may hinder timing. The main objective of this proposal is to study attentional processing of temporal information in the seconds-to-minutes range (interval timing) using combined behavioral, physiological, and computational approaches. Behaviorally, we will study the effects of non-temporal features of events on the re-allocation of attentional and memory resources when subjects time one or multiple durations. At the physiological level, we propose to dissect the neural circuits involved in the interaction between the internal clock and the resource allocation mechanims using neuropsychopharmacological methods, specifically by local infusions of specific agonist and antagonists in key sites of the neural circuit in order to manipulate it and gain knowledge of its functioning. Computationally, we propose to evaluate two models of re-allocation of resources, in order to address the effect of behavioral and pharmacological manipulations on attentional processing of temporal information, and to arrive at predictions that warrant further experimental investigation. The studies will help elucidate the behavioral, neural, and computational mechanisms involved when we pay attention to timed stimuli, and will improve our understanding of the impact of attentional factors on complex cognitive processes that require temporal information, processes which may be disrupted in disorders like Parkinson, Huntington, and Schizophrenia. The results of the project can be used to devise behavioral measures for the early assessment of such disorders, and to understand the cognitive processes disrupted when these substrates are dysfunctional. This information is crucial to assessing the value/efficiency of potential treatment strategies in animal models of such disorders.